The Analytic Core will provide overall statistical and mathematical modeling support for Projects 1-5 of the Program Project. The staff of the Analytic Core will expand upon their work in the previous Program Project to develop and refine methods of time series analysis. To better integrate findings from data collected using a wide variety of experimental designs, time series analysis methods need to be applicable to many data types. Core B will refine time series analysis methods developed during the previous program project to make them useful with many data types, such as the plasma cortisol data to be collected from human subjects and the multi-neuronal activity data to be collected from SCN slices. These time series analysis programs will be designed to not only provide information about circadian phase and period, but will have associated confidence limits. A new focus on the statistical analysis to be provided by Core B will be to introduce transition rate probabilities for quantifying intermittent patterns of behavior, such as sleep/wake in humans and activity/rest in animals. These methods will be key to understanding the impact of the aging process on behavior, and to better understanding the nature of these complex behavioral processes. An essential component of this overall Program Project is to understand the impact of both circadian rhythmicity and the sleep-wake homeostat on age-related changes in human sleep timing and structure. Core B will develop data analysis techniques and refine models for better understanding human sleep pressure. Such techniques will be important for understanding age-related changes in sleep pressure as a function of prior wakefulness, and in understanding how particular physiologic measures relate to actual sleep structure at sleep onset. Finally, Core B will continue the development and refinement of models for human neurobehavioral function to better predict performance and sleep quality under a wide range of sleep schedules. The analysis methods and models to be developed and refined by the Analytical Core will thus be key in interpreting the data from the proposed experiments, and will provide an overall framework for discussion and integration of results from the planned experiments, which span the range from the molecular level to the whole animal level.